Melilite-Type Borates Bi<sub>2</sub>ZnB<sub>2</sub>O<sub>7</sub> and CaBiGaB<sub>2</sub>O<sub>7</sub>
Bibliographic record
Abstract
The bismuth borates Bi 2 ZnB 2 O 7 and CaBiGaB 2 O 7 have been synthesized by solid-state reactions at temperatures in the 650−825 °C range at 1 atm pressure. These compounds are the only synthetic diborate members of the melilite family, A 2 XZ 2 O 7, in which layers of A cations alternate with XZ 2 O 7 tetrahedral layers. Except for CdBiGaB 2 O 7, the synthesis of other substituted bismuth borate melilites has been unsuccessful. The crystal structures of Bi 2 ZnB 2 O 7 and CaBiGaB 2 O 7 have been determined by powder X-ray diffraction and refined by the Rietveld method using powder neutron diffraction data. CaBiGaB 2 O 7 adopts the regular tetragonal melilite structure ( P 4̄2 1 m space group, Z = 2) containing B 2 O 7 tetrahedral dimers. The refinement of split eight-coordinated sites for the Ca 2+ and Bi 3+ interlayer cations suggests the presence of additional disorder. Bi 2 ZnB 2 O 7 adopts a unique orthorhombic melilite superstructure ( Pba 2 space group, Z = 4) containing both tetrahedral B 2 O 7 and triangular B 2 O 5 dimers. The Bi 3+ cations occupy two distinct interlayer sites with strongly asymmetric 6-fold coordination environments. The preliminary measurement of second harmonic generation efficiencies ( d eff ) of powder samples has yielded values of 4.0 (Bi 2 ZnB 2 O 7 ) and 1.6 (CaBiGaB 2 O 7 ) relative to a KH 2 PO 4 standard.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".